Imprint lithography is gaining interest as a viable alternative to more traditional (mask-based) optical lithography techniques employed for manufacture of semiconductor devices, because imprint lithography is able to provide patterning of comparable feature sizes at significantly lower cost.
In soft stamp imprint lithography techniques such as Substrate Conformal Imprinting Lithography (SCIL), a flexible stamp including a relief feature pattern on its surface is brought into contact with a substrate, which typically carries a (curable) resist material to be imprinted by the feature pattern. Thus, in a typical imprint lithography method, the imprint step includes that a layer of resist material on a substrate is brought in contact with the relief pattern surface of the flexible stamp. Following this step, the resist material is developed, e.g. cured to be solidified while still in contact with the relief pattern surface of the flexible stamp. Once solidified, the flexible stamp (and therewith its relief feature pattern) is released from the solidified resist material to leave a patterned solidified resist layer on the substrate.
When using soft stamps for imprint lithography, one way to carry out the imprint step is disclosed in US patent application 20100083855. The method includes that the flexible stamp is locally bent to have a partial area of the stamp surface protrude towards the substrate and create at that protrusion an initial area of contact between the flexible stamp surface and the substrate surface to be imprinted. After such initial contact has been made, the initial area of contact is then grown (e.g. extended) over a larger part of the flexible stamp and the substrate by gradually making further contact at or near the edge of the contact area such that the edge of the contact area moves along the substrate surface. After solidification of the resist material has occurred, release of the stamp is done using the reverse process of gradual breaking of contact.
In order to make such an imprint lithography process as commercially viable as possible, it is desirable to maximize the throughput of such a process. This, however, is far from trivial as increased throughput may compromise the quality of the pattern formed in the resist layer, for instance because the pattern is not accurately transferred, e.g. because insufficient conformal contact between the stamp and substrate is being created, or because an overly rapid release of the feature pattern of the stamp from the developed resist can lead to damage to the developed resist layer or even to the feature pattern on the stamp.
It is known per se that it is possible to individually optimize the throughput of the ensemble of imprinting step and release step of such an imprinting process, i.e. that these steps may be performed at different speeds. Typically, the imprinting step can be performed at higher speeds than the release step. This for instance may be because during the imprinting step the resist material is still low viscous and can flow while on the other hand, the release process is hampered by the interaction between the stamp material and the developed (solidified) resist, which slows down the release process in order to prevent damaging of the flexible stamp during release. This is due to the enhanced surface area between the stamp and the cured resist, which increases the van der Waals forces per unit area.
For instance, it is possible on an imprinting apparatus such as the apparatus disclosed in US patent 20100083855 to set the speed of an imprinting step and to set a different speed for a released step. There is still a further need to improve the throughput of an imprinting process as described above.